This invention relates to welding, and, more particularly, to weld repair wherein the weldment must be terminated within the perimeter ol the article being welded.
It is not uncommon that some articles experience cracking during fabrication or during service. For example, aircraft engine parts may experience cracking during service as a result of applied strains and thermal strains. In addition, parts made of certain alloys, particularly those having low ductilities at temperatures just below the melting point, have a tendency to exhibit through-wall cracking during the initial casting fabrication.
If the surface cracks are not overly severe, they may be repaired by welding. Welding as used in this context means that the cracked material is first removed, usually by grinding. The resulting void is then refilled with molten metal. Upon cooling, the molten metal solidifies so that the crack is filled with solid metal, termed the weldment, and thence is repaired. Extra "filler" metal, usually but not necessarily of the same composition as the base metal of the article, is supplied to the molten region to aid in filling the crack.
The weld repair process generally works well along most of the region of the crack. However, it is sometimes found that the weld repair process induces further cracking of the article, particularly at locations near the point of termination of the weldment. These repair-induced cracks are usually smaller than the original crack that was to be repaired, but are still troublesome and must be repaired.
A typical further repair procedure for the repair-induced cracks is to cap weld over these cracks with a lower-melting-temperature, weak filler material, and then to hot isostatically press the cap-welded region. Another further repair procedure is to fill the repair-induced cracks with a filler metal such as a powder, and then hot isostatically press the article. These repair procedures are suited for the repair of the small repair-induced cracks, but not of the original larger crack. The repair procedures, while operable, are expensive and may introduce material of a foreign composition into the article, as in the case of the cap weld procedure.
There is a need for an improved approach to the weld repair of articles with surface cracks. The present invention fulfills this need, and further provides related advantages.